Screw conveyors for transporting material have existed, in one form or another, for many centuries. A screw conveyor consists essentially for a central rotating shaft and a flight secured about the shaft along helical lines for transporting the material along the shaft when the shaft is rotated.
In modern applications, a screw conveyor may be constructed from separate pieces of metal welded together by many weld joints. While this construction is satisfactory for many applications, a screw conveyor including a large number of weld joints may be damaged if subjected to wide extremes of temperature.
In one application, screw conveyors have been subjected to a temperature range from ambient temperature when the screw conveyor is not in use, to a temperature of 1300 degrees Farenheit when transporting material. The continued expansion and contraction of the screw conveyor due to such an extreme temperature range has often caused breakage of the weld joints. It has been found that the typical screw conveyor will survive only one month of this temperature variation before repair is necessary.